Fix minor compiler warnings

src/backends/R/rhighlighter.cpp

@@ -27,7 +27,7 @@
 #include <QDebug>
 
 const QStringList RHighlighter::operators_list=QStringList()
-   << QLatin1String("(\\+|\\-|\*{1,2}|/|&lt;=?|&gt;=?|={1,2}|\\!=?|\|{1,2}|&amp;{1,2}|:{1,3}|\^|@|\\$|~)")
+   << QLatin1String("(\\+|\\-|\\*{1,2}|/|&lt;=?|&gt;=?|={1,2}|\\!=?|\\|{1,2}|&amp;{1,2}|:{1,3}|\\^|@|\\$|~)")
    << QLatin1String("%[^%]*%"); // Taken in r.xml syntax file from KSyntaxHighlighter
 
 const QStringList RHighlighter::specials_list=QStringList()

src/backends/maxima/maximasession.cpp

@@ -192,7 +192,6 @@ void MaximaSession::reportProcessError(QProcess::ProcessError e)
 void MaximaSession::currentExpressionChangedStatus(Cantor::Expression::Status status)
 {
     Cantor::Expression* expression = expressionQueue().first();
-    const QString& cmd = expression->command();
     qDebug() << "expression status changed: command = " << expression->command() << ", status = " << status;
 
     switch (status)

src/lib/renderer.cpp

@@ -165,6 +165,8 @@ QImage Renderer::epsRenderToImage(const QUrl& url, double scale, bool useHighRes
         *errorReason = QString::fromLatin1("Render Eps on Cantor without eps support (libspectre)!");
 
     Q_UNUSED(url);
+    Q_UNUSED(scale);
+    Q_UNUSED(useHighRes);
     Q_UNUSED(size);
     return QImage();
 #endif

src/mathrendertask.cpp

@@ -177,7 +177,7 @@ void MathRenderTask::run()
     // For example, this pdf will copied into .cws file on save
     const QString& pdfFileName = pathWithoutExtension + QLatin1String(".pdf");
 
-    bool success; QString errorMessage; QSizeF size;
+    bool success; QString errorMessage;
     const auto& data = renderPdfToFormat(pdfFileName, m_code, uuid, m_type, m_scale, m_highResolution, &success, &errorMessage);
     result->successful = success;
     result->errorMessage = errorMessage;